Ishaan ate 1 slice of cake. Christopher ate 3 slices. If Ishaan ate $\dfrac{1}{9}$ of the cake, what fraction of the cake is remaining?
Explanation: If 1 slice represents $\dfrac{1}{9}$ of the cake, there must have been a total of 9 slices. $\text{fraction of cake remaining} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 4 slices, which leaves 5 out of 9 slices remaining. There is $\dfrac{5}{9}$ of the cake remaining.